Microbes anaerobic

Aerotolerant anaerobes Microbes that grow under both aerobic and anaerobic conditions, but do not shift from one mode of metabolism to another as conditions change. They obtain energy exclusively by fermentation. 

CODH/ACS is an extremely oxygen-sensitive protein that has been found in anaerobic microbes. It also is one of the three known nickel iron-sulfur proteins. Some authors would consider that there are only two, since the CODH and ACS activities are tightly linked in many organisms. However, there is strong evidence that the ACS and CODH activities are associated with different protein subunits and the reactions that the two enzymes catalyze are quite different. CODH catalyzes a redox reaction and ACS catalyzes the nonredox condensation of a methyl group, a carbonyl group, and an organic thiol (coenzyme A). 

As pointed out earlier a third class of B12-dependent enzymes, present in anaerobic microbes, carry out reductive dehalogenation reactions, which play an important role in the detoxification of chlorinated aliphatic and aromatic compounds, among which are many important man-made pollutants. The role of B12 in this class of enzymes is not clear— possibly by formation of an organocobalt adduct, as in the case of methyltransferases or alternatively by the corrinoid serving as an electron donor. 

Anaerobic microbes in the presence of water in the landfill will consume these natural products and produce methane, CO2 and humus. One study reported the average composition of 20 year old refuse to be 33 % paper, 22% ash and 12% wood [18]. Thirty core samples revealed a wide range of degradation and microbial activity that were directly attributed to sample moisture content. Recovered polyethylene degradation was evaluated and determined to be as high as 54 %. 

Jenney FE Jr, Verhagen MFJM, Cui X, Adams MWW. 1999. Anaerobic microbes oxygen detoxification without superoxide dismutase. Science 286 306-9. 

Some of the missing nitrogen is also likely due to the anammox reaction, in which ammonia is oxidized to N2 by anaerobic microbes. 

Gibson J. and Harwood C. S. (2002) Metabolic diversity in aromatic compound utilization by anaerobic microbes. Ann. Rev. Microbiol. 56, 345-369. 

Fig. 6. Sequestration of redox power in microbial mats. An atmosphere-ocean system containing CO2, NO2 and SO2 would supply oxidation power to the water (e.g as NOJ, SO ). Microbial mats finely focus and control the redox boundary, so that it becomes a sharp plane rather than a diffuse zone. Above the boundary, rubisco-using bacteria, both photosynthetic and non-photosynthetic, provide reduced organic matter. Below the redox transition, anaerobic microbes recycle the oxidation power, returning chemical species such as CH4, H2S and NH3 to the upper levels. The deeper levels of the mud become a long-term store of reduction power (e.g. methane-rich sediment), sequestered from the atmosphere and inaccessible to it until recycled by large-scale geological processes such as subduction.

In the absence of O2, competition among anaerobic microbes for electron donors sets up a series of alternative terminal electron-accepting processes in the order NO reduction, Mn(lV) reduction, Fe(III) reduction, SO -- reduction, and methanogenesis (Figure 9.2 Ponnamperuma, 1972 Megonigal et al., 2004). To a lirsi approximation, a single terminal electron-accepting process dominates... 

Both aerobic and anaerobic microbes generate most of the ATP by oxidative phosphorylation. However, the terminal electron acceptor, energetics, and kinetics are different for aerobic and anaerobic microorganisms. 

How would you expect the activity level of anaerobic microbes to compare with that of aerobes Why ... 

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